This invention relates to a control valve for a hydraulic brake booster having a shuttle member with a first end to control metering of pressurized fluid to an actuation chamber during a brake application and a second end to control metering of pressurized fluid from the actuation chamber to a reservoir on termination the brake application.
In hydraulic brake boosters of a type disclosed in U.S. Pat. Nos. 4,281,585; 4,539,892; 4,625,515; 6,561,596 and U.S. Pat. No. 6,732,578, a control valve is located in a first bore and a power piston is located in a second bore of a housing. A lever arrangement is connected to the power piston and the control valve. An input force applied to a brake pedal by an operator acts on the lever arrangement to develop a manual mode and a power assist mode of operation. The lever arrangement pivots on the power piston and communicates an actuation force that moves the control valve to regulate the flow of pressurize fluid from a source to an operational chamber. The regulated pressurized fluid supplied to the operational chamber acts on the power piston in the first bore to develop an operational force that pressurizes fluid that is supplied to wheel brakes to effect a corresponding brake application. A reaction force produced by regulated pressurized fluid in the movement of the power piston is transmitted back to the brake pedal to balance the input force such that the operational force supplied to move the power piston in the first bore is a function of the input force applied to the brake pedal.
Additional features such as traction control, dynamic operational control and anti-skid control under the control of an ECU have been added to hydraulic brake booster to provide a total brake system. During an ECU generated brake application, the brake pedal of the hydraulic booster may mirror the movement of the power piston. In addition, as a result of the rapid opening and closing of the control valve during a ECU generated brake application, an increase in the level of noise created as pressurized fluid flows to the actuation chamber and on released from the brake chamber may occur. Structure to hold a brake pedal stationary during an ECU generated brake application is disclosed in U.S. Pat. No. 6,203,119 wherein a control valve seat moves to meter pressurized fluid; in U.S. Pat. No. 6,732,518 where a separate piston is provided to act on the control valve to meter pressurized fluid; and in U.S. application Ser. No. 10/767,300 wherein a sleeve acts on the control valve to meter pressurized fluid to effect a brake application but it would not appear that the creation of noise has been specifically addressed in the known prior art.